Feeding my Brooklyn DAC+: iMac with 10m USB extension or ROCK Nuc with shorter cable? Sound Qualiy?

[ix400]

Hi,

 

today I received my new Brookly DAC+. I would like to use it with Roon, the Roon Core is installed on my iMac. However, the iMac is located about 10m away from the place where the DAC+ is located. 

 

For connection of the DAC to the MAC via USB I was trying to use the following 10m USB A/B cable:

https://www.amazon.de/gp/product/B00XHVB9A4/ref=oh_aui_detailpage_o03_s00?ie=UTF8&psc=1

 

However, the connection seems to be not stable enough. When I e.g. play MQA files from Tidal, the green MQA-indictaor is blinking once in a while and switches between MQA „on“ an „off“. 

 

Therefore, I tried the following USB-extension cable which has sort of a repeater/amplifier function:

https://www.amazon.de/gp/product/B007BM90E2/ref=oh_aui_detailpage_o03_s00?ie=UTF8&psc=1

 

To this extension cable I simply connected the USB A/B cable that came with the Brooklyn. It seems to work much better than the cable from my first attempt, the MQA signal is now stable. 

 

However, I am wondering if the 10m long repeater cable might somehow negatively influence the overall sound quality. Does such a repeater cable introduce jitter? 

Would it be better to setup a Roon ROCK Nuc that I can place directly next to the DAC+?

 

I really would appreciate If you could share your thoughts on this. 

Have a good weekend,

Chris

[mansr]

10 metres is a lot for a USB cable, so it's hardly surprising that doesn't work reliably. The standard actually specifies a maximum cable propagation delay of 26 ns, so anything longer than about 5 m is automatically not compliant. Although this alone is unlikely to cause any real problems, the driver circuits will not be designed for such a long cable, so signal integrity might be problematic. This is likely why the active cable works better.

 

As for sound quality, if the cable is marginal, you may get the occasional tick or brief drop-out. If this doesn't happen, it's all fine. A long USB cable will not cause the kind of degradation associated with poor analogue interconnects. That said, spread-out system like that will be prone to ground loop issues, typically manifesting as hum. Again, if you don't notice anything obviously wrong with the sound, I wouldn't worry about it.

 

Another alternative is to use a USB over Ethernet extender. This avoids all the problems of a long USB cable without introducing another computer into the mix.

[Ralf11]

you might also contact the manf. for other ideas, and how sensitive the DAC is to EM noise from ground loops, or jitter

 

 

[57gold]

Long USB cables are NOT on/off items.  They can "function", that is you might hear continuous music with a long cable, which is longer than 2 meters, but versus a 1 meter cable the music will suffer.

 

How do I know this?  Purchased and installed a 4 meter cable by manufacturer recommended by Ted (one of CA's resident experts and good guy) believing that length didn't matter and it worked with my room.  Spatial cues, timing, cymbals, PRAT...all messed up, really awful sound with the 4 meter cable versus the 1 meter.  Returned that cable and re arranged my system.

 

[ix400]

Thank you very much for all your answers.

 

Could an USB ethernet extender be a jitter free solution? Or does the USB > Ethernet > USB conversion also impair the sound quality?

[marce]

A USB hub can extend the cables, two 5m with the hub in the middle, again as Mansr (Troll, lol)has mentioned, the receivers and more importantly the drivers may not be up to the job. USB transeivers are designed to drive s signal down a 5m max cable, if you look at an eye diagram of the signal after 5m, the eye opening will be smaller than a 1m cable, but still within the required spec, every metre of cable extra will reduce the eye opening till eventually you will get issues.

This reminds me of a design we once worked on, a remote relay box, the trouble was the sales team specified it had to work up to 1km from the main unit! (seriously 1000m, because the competition claimed the same). With the right driver circuitry (LowishVDS, circuitry to check for open and shorted cables) we got 200m down unshielded figure of 8 and the full 1km down some rather expensive Beldon shielded cable. The only problem as we pointed out to the sales team was the unit cost £300, the cable £5,000! But it does show how robust a digital signal can be, even when pushed well past it's recommended specification.

With USB I would keep within the spec, then your not adding issues, such as noise pick-up. every extra metre of cable lowers the possible rf frequencies it may pick up. If your using the 5Vs supply it can be even worse as your adding extra inductance in the power feed and the return (0V) line, which is also used as a digital return path for the USB single ended handshaking signals (these are more likely to suffer rather than the data being single ended signals rather than LVDS).

[marce]

3 hours ago, ix400 said:

Thank you very much for all your answers.

 

Could an USB ethernet extender be a jitter free solution? Or does the USB > Ethernet > USB conversion also impair the sound quality?

With a robust data path from source to DAC such as USB where the data is buffered before the DAC, jitter is only an issue at the point of conversion, or more specifically at the DAC's input pins. To be honest with todays high speed comms. it shouldn't be that hard to lay out an Audio DAC with SMD components with such short signal paths that jitter should be a zero issue, I suspect with most competently designed DAC's it isn't.  ADC;s; DAC's are everywhere, not just audio, its how we measure and record the analogue world we live in, control the mass communications we use, measure the impossible (gravity waves for eg.), we can do multi channel 24bit ADC/DAC's working in the MHz so the basic audio conversion should be pretty easy these days...

[Panelhead]

  I recently tied a long (10 meter) fiber cable. I was a big downgrade compared to a 0.5 meter copper cable. Huge disappointment. 

  I cannot hear the difference between a 1/2 meter and 2 meter cable. But over 2 meters you are pushing it.

[ix400]

With respect to my opening post:

 

Maybe it is also possible to use my Mac Mini via Ethernet as Roon Bridge/Endpoint? I could place it directly next to the DAC and connect it with a short USB cable.

 

Roon Core could then remain on the iMac. 

 

What do you think? Would the chain „Core >> Bridge >> DAC“ impair the sound quality? 

[Ralf11]

re: impair the sound quality - I'd worry more about galvanic isolation in the USB cable allowing EM noise from the mini to get into the DAC

[ix400]

... so you mean I need a special USB cable that does this galvanic isolation? Is there a cable that you can recommend?

[Ralf11]

it might be done in your DAC - some use optical isolators; maybe ask the manf. re the Brooklyn (it is well regarded and not inexpensive so my bet would be they took care of it for you - maybe...)

 

if the music formats are not too DSDy you could buy a Schiit Eitr

 

other options include using Cu Ethernet or optical

 

or... listen carefully, blind, on the right test music ---> that is the really confirming overall test